The basic Formula Ford small-tube space frame chassis is a simple and well proven type of chassis, inexpensive to manufacture and relatively easy to repair when damaged. The earliest space frame designs for racing cars were developed by Cooper, Mercedes Benz and Lotus in the mid 1950's and refined over the following decade. The original Lotus F3 chassis design of 1957 was adapted for the first batch of FF cars in late 1958 powered by the Cortina GT engine.
These chassis were typically made with mild steel round and square tubing which formed the longitudinal members with a number of shorter members running between them with extensive triangulation. These tubes were generally brazed together but later, tig and mig welding became the norm. Chassis strength and torsional rigidity relied on triangulation, small gusset plates and a rigid belly pan rivetted to the underside of lower members.
Later FF chassis - beginning with the Swift DB-1 of 1983 - used much stronger chrome moly tubing.Early FF chassis had far less strength and rigidity than more current designs as can be seen in the accompanying photos. Some particular chassis were known for lightness and as a result, the extent of rigidity and degree of protection they offered was minimal. A good example would be the Lola 342, the upper rails of which were made from light gage sheet metal! In the US, "strengthened" Lolas performed better due to greater torsional rigidity which increased the tires' grip and allowed the suspension to act more effectively. Late seventies cars were far stronger in every area. Two good examples would be the Zink Z10 - known for its robustness - and the Crossle 32/35 series. Cars built from the early 80's on - and certainly all current chassis - have far more sophisticated designs with more members in key locations and much more triangulation.
Driver protection and torsional rigidity became major design criteria in cars like the Swift, Reynard and Van Diemen. The Swift, designed in 1982, was a revolutionary car in many ways and was the first to maximize strength and driver safety by having an assembly of tubes which virtually enclosed the cockpit with tubes placed above the driver's shoulders.
Formula Ford chassis protect the driver in various ways and to varying degrees depending on a broad rage of factors: overall configuration of the particular design, the vintage of the design, the number, size and location of the tubes as well as the quality of the materials and welds. Age and the modifications that may have been done to it over time will affect its condition and strength. During the first decade of the class, many of the cars used the longitudinal chassis tubes to transfer water from engine to front mounted radiators. Over time, corrosion and deterioration of these tubes can significantly reduce their strength and, where possible, they should be replaced entirely.
A lightweight formula car is meant to be rigid but it is also designed to absorb crash energy by means of "local-deformation" when a car hits a solid, relatively immovable object. In cases where there is suspension impact, cars are designed with tabs or shear plates so that components can tear off without inflicting major damage to the chassis itself. As a consequence, current designs offer a high degree of protection under the kinds of crash conditions which can occur because crash energy is absorbed by progressive deformation and because the driver's compartment is now so strongly enclosed.
Anyone purchasing an older Formula Ford should minimize the level of risk by selecting a chassis design known for its strength or by engaging a qualified race prep shop and incorporating additional braces. First, check to be sure everything is still in place as it was manufactured and check the condition of the chassis. In some cases, additional members can be added and there are chassis specialists and prep shops that are well equipped and have experience with such modifications. Older cars may also require new front roll hoops and new main roll hoops to meet current regulations. (see the "Buying a Used Formula Ford" page)
The chassis of the Citation-Zink Z16 - a Zink/Lathrop creation - is a good example of the generation of chassis designs from about 1978 up through 1983 which had additional triangulation, stout front roll hoops and additional side protection for the driver. The next generation of cars is symbolized by the Swift DB1 which had high side cockpit bars and a far greater degree of torsional stiffness.
The chassis of the Swift DB1, designed and built in California in 1982-83, was a radical departure from all previous Formula Ford chassis designs, incorporating very extensive triangulation and upper bars at the cockpit - in a very narrow configuration. The radiator was positioned behind the main roll bar which pushed the driver forward. An ingeniously designed cast aluminum bell housing contained the oil sump tank and the rear spring/shock assemblies. The David Bruns design was the ultimate optimization of the FF1600 chassis rules and changed Formula Ford forever.
The Ed Zink design for the Citation-Zink Z16 chassis was developed in 1978 and featured three top-to-bottom hoops and a removable rear subframe for the engine/transmission combo.
This detail of a mid-1990's Van Diemen chassis shows the extent of diagonal bracing from just in front of the dashboard toward the front. Because this design incorporated the shocks and springs located in the area above the driver's knees, extensive bracing achieved the maximum torsional rigidity of the chassis and also assured that there was no compliance in the suspension components.
Formula Ford Chassis Fundamentals
Chassis Design and Construction
Frame-up Rebuilds
Racing Car Preparation, Tuning and Engineering - Carroll Smith's Books
Mark Donohue's "The Unfair Advantage"
At one time or another Carroll Smith was race engineer for cars driven by Andretti, Foyt, Gurney, Hulme, Ickx and McLaren. Cars he engineered and teams he managed won LeMans and the Manufacturer's World Championship. He was a passionate racer, an articulate speaker and an excellent writer who books demonstrate the breadth of his knowledge, his dedication to the sport, his zest for life and his sense of humor. Smith changed the entire approach to race car preparation forever when he published the first of his superb books - PREPARE TO WIN - in 1975, a book which had a tremendous impact. Interestingly, most of the chapters had been published in the very best of the automobile racing magazines being published in the late 60's and early 70's, SPORTS CAR GRAPHIC. With this one book in hand, the amateur racer had access to all the accumulated knowledge that Smith had applied over his many years as driver, mechanic, race engineer and team manager. PREPARE TO WIN provides a mountain of information to anyone rebuilding or preparing their car for battle and even today, 32 years later, its value is undiminished. Typically, anyone using this book while doing a "frame-up" rebuild would be alerted to twenty or thirty items that, were they not seen and addressed, could potentially cause a failure or a sure DNF! Following on the great success of the first volume in his series, Smith added to the literature by writing TUNE TO WIN and then ENGINEER TO WIN, each of which took topics raised in the earlier volume to new levels of detail. TUNE TO WIN is the ultimate source of guidance for proper chassis design, assembly, adjustment and tuning while ENGINEER TO WIN is a comprehensive treatise on materials, fabrication and hardware. Smith followed those books with a smaller volume which covered plumbing and fasteners in greater detail and then he wrote ENGINEER IN YOUR POCKET. Lastly, he wrote the truly great DRIVE TO WIN, a very insightful exploration and explanation of how to drive fast, how to compete and how to get the car to do what you want it to do.Carroll Smith, the original "race engineeer" stood alone at the top of his field and he unselfishly shared everything he learned with racers at all levels of competition. Amateur racers, in particular, owe him a big debt of gratitude.
Frame-up Chassis Rebuilding
Carroll Smith
The great race engineer and his fantastic books
You bought a well used Formula Ford. Now what to do? If the car looks a little tired, a frame-up rebuild may be called for. How else to make sure everything is the way it should be? A complete rebuild is a chance to check every component, every single fastener, every plumbing line. A typical open wheel race car can be disassembled in a few days' time. But keep in mind that it is during a careful disassembly process that the condition of every part can be determined, degree of wear can be measured, cracks can be found and unsatisfactory assemblies can be analyzed so new configurations can be planned. Develop a plan, make up a note book and load a new chip in the digital camera because you'll want to record every part to facilitate reassembly. Over time, changes can creep into every race car and while disassembling it, you will undoubtedly find things that can be improved, other things that can be returned to their proper, original state or components that just plain need to be replaced. The condition of every wire, every hose, every bolt must be reviewed. Likewise some rod ends and spherical bearings will be found to be over their wear limit and each one should be carefully looked at. Maybe the seating position needs work to make it right to improve your own comfort and to increase its safety. Stripping the chassis itself may reveal cracks or bent members or, at worst, a tweaked chassis which would make alignment difficult. A checklist for a frame-up rebuild can be found below and a great source of information is Carroll Smith's first and most valuable book, PREPARE TO WIN, which is chock full of insights into the whole process of preparing a a car for the track. (see the "Buying a Used Formula Ford" page)
This Lola 342 chassis, built by Eric Broadley's company in 1976, is about to undergo a complete frame-up rebuild. As step one, the bodywork, engine and transmission have been removed and before long, every single component and every fastener will be removed, inspected, cleaned and refurbished. The design which was distinguished by the use of sheet metal for the upper rails which helped it achieve a remarkably low total weight of about 80 pounds. These cars were known as "flexi-fliers" because the chassis was designed to flex and, in essense, act as a "fifth spring". In the US, many of them were stengthened by the introduction of longitudinal tubes or continuous metal closures on the underside of the open top rails and the introduction of a number of other supplementary chassis tubes and gussets.As part of this modification, the spring rates were reduced significantly. Both versions won a lot of races through about 1981 when the car was eclipsed by newer design from Crossle and VanDiemen. As a classic of their era, the Lola 342 is a much sought after car.
Mark Donohue's book "The Unfair Advantage" chronicles this great American driver's years in racing with special emphasis on the lengthy period he spent at Penske racing where a string of race winning cars were developed and perfected under his direction. These exceptional cars brought numerous race wins and championships to the team. Donohue had an engineering degree from Brown University and he was also a gifted driver. The combination of his engineering knowledge, Roger Penske's penchant for perfect car preparation and the many "unfair advantages" they dreampt up meant their's was a very difficult team to beat. This book tells the whole story of the Indianapolis victory, many wins in Trans-Am and.of course, the triumph of Penske's 917-10 and 917-30 in the Can-Am series.
This is the same chassis a month later. The chassis was glass-bead cleaned, crack checked and repaired in a few places. A few steel gussets have been added, a new steel belly has been installed and the entire chassis has been repainted.
Formula Ford Chassis Fundamentals
The Unfair Advantage
Here, the suspension components have been fitted to the completed chassis and the bodywork has been stripped, refinished and primed before being refitted to the chassis.
Lola 342
Chassis Design and Construction